Adsorption:Multicomponent

From Wiketomica
Introduction
Background
Examples
Problems
Run Simulation
References
Credits
Assessment
Etomica Modules

We can treat adsorption from a mixture of gases (at low pressures) by extending the Langmuir isotherm:

These reactions are not independent because both species compete for the same surface sites. The two equilibria must be solved simultaneously:

As for the one-component case, we define surface coverages and , and note that

, or

Then,

and dividing, we get

The ratio of A:B on the surface is therefore different than the ratio of A:B in the gas phase, by precisely , so the more strongly adsorbed component is enriched on the surface. This is referred to as the thermodynamic selectivity, the preference of the surface for one species of a mixture, and is the basis for many techniques to separate gas mixtures.